Rotary sprinkler heads are known which comprise a nozzle that rotates in a circle, or a portion thereof, for watering the arc segment subtended by the angular rotation of the nozzle. Typically, the sprinkler head is able to rotate unidirectionally when it rotates in a full 360.degree. circle. However, when it waters less than a full circle, such as an arc segment of 120.degree., the sprinkler nozzle must reverse rotational direction at each end limit of the arc segment to sweep back and forth over the arc segment.
U.S. Pat. No. 3,107,056, issued Oct. 15, 1963, discloses a rotary sprinkler head of this general type. In this patent, the rotatable nozzle is keyed to a gear that is driven by a gear train which can be shifted to bring one of two final drive gears into engagement with the driven gear. Each of the final drive gears is rotating in a different direction so that the driven gear will be rotated in different directions depending upon which of the final drive gears is swung into engagement with the teeth on the driven gear. The shifting movement of this drive assembly is accomplished by means of a trip arm which engages against one of two stops. The first stop is mounted on the driven gear itself. The second stop is mounted on an adjusting ring that overlies the driven gear and which is normally carried with the driven gear for rotation therewith. The distance between the first and second stops determines the angular extent of the arc segment being watered.
The sprinkler head referred to in this prior patent disclosed a means for rotating the adjusting ring relative to the driven gear to adjust the distance between the stops and hence the distance of the arc segment being watered. This mechanism comprises a spring loaded button or plunger which could be biased inwardly against the bias of the spring to engage one of a number of perforations in the adjusting ring. When this was done, the operator was then able to grab and manually rotate the nozzle, and hence the driven gear, relative to the adjusting ring which was prevented from rotating through its engagement with the plunger. The relative rotation between the adjusting ring and the driven gear would vary the circumferential distance between the stops carried on each. This type of structure has been used in many of the rotary sprinkler heads manufactured and sold by The Toro Company of Minneapolis, Minn., the assignee of the present invention. Such sprinkler heads include the Super 600.RTM. sprinkler head.
While the above-noted method is effective in causing the distance between the stops to be adjusted, it has a number of disadvantages. For one thing, it requires two hands by the operator, one to hold the button inwardly and the other to manually turn the nozzle structure. This can be difficult to do. Moreover, it is relatively easy for an outsider to get access to the button so that vandals could easily readjust the arc segments after an installer had first set them. This would, of course, require the installer to come back and readjust the arc segments which is a laborious and time-consuming process.
A newer sprinkler of this general type has been made and sold by Hunter Industries and is known as the Series 75 sprinkler. In this sprinkler, the nozzle structure and drive assembly are part of a riser that pops up out of the sprinkler head body under the influence of fluid pressure. Except for the nozzle opening, that portion of the riser which extends above the body level in the popped up position of the riser is substantially enclosed so that the interior of the riser is difficult to gain access to. The driven gear and adjusting ring structure are contained in the interior of the riser.
However, the problem remains of adjusting the distance between the stops on the driven gear and the adjusting ring for adjusting the extent of the arc segment. This is accomplished in the Hunter sprinkler by having a keyhole-shaped opening in the top cover of the riser which leads downwardly into the interior of the riser. This opening allows a keyhole-shaped tool, i.e. a screwdriver-like tool with a head having two outwardly extending ears in the shape of a key, to extend downwardly into the riser housing. The end of this tool is engageable with a gear that is engaged with a gear structure on the outside of the adjusting ring. Rotation of the tool will rotate this gear, and hence the adjusting ring, to cause the adjusting ring to move relative to the driven gear and change the distance between the stops.
The solution embodied in the Hunter sprinkler head does not solve the problem of vandal-resistance. While enclosing the driven gear and adjusting ring inside the riser and requiring the use of an elongated tool to adjust the two is somewhat more effective than some prior art structures, the Applicant has found that any elongated tool, such as a plain screwdriver, is often effective for reaching down and actuating the drive gear that causes rotation of the adjusting ring. Accordingly, it would be possible for vandals to maliciously readjust the Hunter sprinkler head simply by using an ordinary screwdriver. This then requires the sprinkler installer to come back out and readjust the arc segments which is obviously disadvantageous. Moreover, the use of a special tool to adjust the stops is a disadvantage. Such tools tend to get lost. If the installer does not have it with him, he is not able to accomplish the necessary stop adjustment.